Previous work in this Branch has elucidated the neuroanatomical pattern of c-fos mRNA expression with the development of amygdala kindled seizures. This project extends that line of investigation to the expression of mRNAs of peptides during kindling and their relationship to c-fos induction. mRNA levels of somatostatin, enkephalin, dynorphin, and thyrotropin releasing hormone (TRH) were measured by in situ hybridization at different stages of kindling. Somatostatin, enkephalin and TRH mRNAs all increase, but dynorphin mRNA decreases with kindling. Each has a different pattern of activation or inhibition at the various stages of kindling. For instance, somatostatin mRNA increases in the cortex after a stage 1 seizure, while enkephalin and TRH increase in the pyriform and entorhinal cortices following stages 1 and 5 seizures. TRH also increases in the dentate gyrus. Dynorphin decreases in the dentate gyrus after stage 5. The pattern of TRH mRNA expression most closely resembles that of c-fos. This suggests that c-fos and TRH expression in kindling may be related and that they may both be found in the same neurons in certain populations of cells. Double labeling of TRH and c-fos is just the beginning.